Sen. Ted Cruz, R-Texas, and Rep. Paul Ryan, R-Wis., penned a joint op-ed for the Wall Street Journal Wednesday calling on Congress to pass Trade Promotion Authority legislation. The two conservative lawmakers argue that the legislation, also known as "Fast Track," is urgently needed to strengthen the U.S.'s ability to negotiate future trade deals.

"By establishing TPA, Congress will send a signal to the world. America's trading partners will know that the U.S. is trustworthy and then put their best offers on the table. America's rivals will know that the U.S. is serious and won't abandon the field," Cruz and Ryan wrote.

The op-ed comes as many conservatives are torn over whether to support the legislation. While historically the right has usually favored free trade, some groups are expressing qualms over it this time around, in large part because it involves ceding congressional authority to the White House.

Fast Track would prohibit Congress from amending trade deals, limiting it to a strict up or down vote on passage. The White House argues the legislation is needed to strengthen its hand in future trade negotiations. Without it, they cannot assure foreign leaders that any deal they strike won't be picked apart by Congress.

Previous presidents from Gerald Ford to George W. Bush had versions of Trade Promotion Authority. The most recent version expired in 2007. Ryan is a co-author of the version introduced last week to revive it.

President Obama wants Congress to pass Fast Track before it brings the Trans-Pacific Partnership, a recently-negotiated deal involving 12 Pacific Rim nations, to Congress for a vote.

The debate has scrambled the unusual partisan lines in Congress. Obama has the support of both Speaker John Boehner, R-Ohio, and Senate Majority Leader Mitch McConnell, R-Ky., on Fast Track but is facing a rebellion from liberal democrats.

Some conservative groups are balking too. "We've been supportive in the past, but conservatives have some understandable concerns not only with the current president but with the concessions Republicans are making on the front end," said Dan Holler, spokesman for Heritage Action.

Ryan and Cruz argue the current version of fast track address those concerns.

[B]efore anything becomes law, Congress gets the final say. The Constitution vests all legislative power in Congress. So TPA makes it clear that Congress—and only Congress—can change U.S. law. If the administration meets all the requirements, Congress will give the agreement an up-or-down vote. But if the administration fails, Congress can hit the brakes, cancel the vote and stop the agreement.

Trade-promotion authority will hold the administration accountable both to Congress and to the American people. Under TPA, any member of Congress will be able to read the negotiating text. Any member will be able to get a briefing from the U.S. trade representative's office on the status of the negotiations—at any time. Any member will get to be a part of negotiating rounds. And most important, TPA will require the administration to post the full text of the agreement at least 60 days before completing the deal, so the American people can read it themselves.

Critics counter that Congress already has the power to reject deals and all Fast Track does is strip lawmakers of the ability to change the deal before passage.